Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a familial heterogeneous clinical and molecular disease characterized by dilatation and dysfunction of the right ventricle and ventricular arrhythmias. The ventricular arrhythmias are heart rate and catecholamine dependent. There may also be involvement of the left ventricle. The diagnosis of ARVC is critical because therapy including implantable defibrillators may prevent sudden death. However identification of subjects at risk remains a major challenge due to limitation of imaging and diagnostic techniques. The proposed study is designed to investigate subjects at risk for ARVC because of a positive family history. Studies will include magnetic resonance imaging, investigation of the utility of a novel diagnostic test, and genetic studies. A protocol has been submitted to the Institutional Review Board.